The respiratory burst oxidase is the enzyme responsible for the production of O2- by stimulated phagocytes. A highly complex enzyme composed of many component parts, it catalyzes the oneelectron reduction of oxygen to O 2- at the expense of NADPH. One of its components is an NADPH-binding polypeptide that is found in the cytosol of resting neutrophils but is transferred to the plasma membrane when the cells are activated, thereby assembling the electron transport chain of the enzyme. The goals of the project described in this application are the purification and characterization of this NADPH-binding component and the study of its interaction with other components of the oxidase. Through this work it may ultimately be possible to develop a sufficiently detailed molecular understanding of the operation of the respiratory burst oxidase to allow the development of a new class of anti-inflammatory agents that work by specifically controlling the production of reactive oxidants by phagocytes.